Stem cells play key roles throughout the life cycle of most multicellular organisms. This application requests funds to support five predoctoral and two postdoctoral trainees per year, in a university-wide Training Program on the biology of Stem Cells and Cell Lineage Specification. Training focuses on the analysis of cellular, molecular and genetic aspects of stem cells and the specification of individual cell lineages to which stem cells give rise. The establishment of a specific Training Program in this research area falls in line with initiatives Columbia University aimed strengthening and expanding its research program in stem cell biology. The training faculty consists of a small and distinguished group of 15 principal investigators that are affiliated with eight departments and programs. Reflecting a good mix of junior and senior faculty, four faculty members are HHMI Investigators and four are junior faculty. Six faculty members study the vertebrate nervous system, five faculty members use a variety of cell fate decisions in simple, genetically tractable model organisms and four faculty members study stem cells and cell lineages outside the nervous system, namely the immune system, epidermis and cancer cells. The training faculty, therefore, does not only reflect a strong cross-section of the outstanding neuroscience community here at Columba University, but also reflects a multifaceted approach to the subject in a variety of different cell types, using a wide spectrum of different methodologies and model systems. Predoctoral trainees will be selected from a pool of candidates that have been recruited via acceptance through a number of strong and selective graduate programs at Columbia University and postdoctoral candidates will be selected via application to the training committee. Specifically tailored course work, a seminar series, a program retreat and a New York City Stem Cell Discussion Group will ensure high quality training and broad exposure of the trainees to recent advances in the field. Faculty and trainees will interact intensively through a variety of mechanisms. With its focus on stem cell biology, our Program will not only prepare trainees for a productive career in the sciences but will also give them the opportunity to be prepared for a future engagement in an area of the biomedical sciences that is of obvious clinical relevance.